Paper manufacturing roll constructions and processes



Aug. 12, 1969 P. J. MITCHELL, JR 3,460,222

PAPER MANUFACTURING ROLL CONSTRUCTIONS AND PROCESSES Filed Dec. 30, 1966INVENTOR.

WW2- mm #0422;

ATTORNEYS United States Patent 3,460,222 PAPER MANUFACTURING ROLLCONSTRUC! TIONS AND PROCESSES Paul J. Mitchell, Jr., Grifiin, Ga.,assignor to SW Industries, Inc., Newton, Mass., a corporation ofMassachusetts Filed Dec. 30, 1966, Ser. No. 606,412

Int. Cl. D21f 3/08 US. Cl. 29-120 4 Claims ABSTRACT OF THE DISCLOSURE Ina paper making machine, following casting of the aqueous pulp suspensiononto a moving web and partial drainage of water therefrom to form a wetsheet, water is pressed from the wet sheet by rolls that arecharacterized by a covering composed of an elastomer and a dispersion ofhydrophobic fiber strands penetrating through the outer surface of theelastomer. Such rolls have superior release characteristics with respectto the wet sheet.

SUMMARY OF THE DISCLOSURE The present invention relates to paper makingmachines and processes and, more particularly to enhancement of therelease characteristics of rolls in contact with the advancing wet sheetfollowing casting of the aqueous pulp suspension in any of the severaldifferent types of paper forming processes. In a typical paper makingprocess, a dilute aqueous slurry of cellulose fibers, which have beenproduced by grinding wood pulp or the like, first is cast on an endlesswire screen through which water is drained, next is advanced onto anendless felt, with which it passes between a series of so-called pressrolls that squeeze and withdraw water therefrom, next is advanced byitself between a series of press rolls and then is advanced over heateddrying cylinders. Difiiculties have been encountered as a result of atendency by fibers of the wet sheet to adhere to the press rolls withwhich they come in contact.

The primary object of the present invention is to provide improverelease characteristics in the rubber cover of a press roll for papersheet formation by the addition of fine fiber strands, ends of whichpenetrate and protrude through the finished, ground outer surface of therubber cover. It is believed that, when the fibers are hydrophobic, thesurface tension of a water film on the rubber cover surface isinterrupted in such a way as to decrease adhesion of the wet paperfilaments to the rubber cover surface as a whole. Other objects of thepresent invention will in part be obvious and will in part appearhereinafter.

DESCRIPTION OF THE DRAWINGS The invention accordingly comprises thedevices and processes possessing the particular components, steps andinterrelationships, which are exemplified in the following detaileddisclosure, the scope of which will be indicated in the appended claims.For a fuller understanding of the nature and objects of the presentinvention, reference is to be had to the following description taken inconnection with the accompanying drawings, wherein:

FIG. 1 is a distorted cross-sectional, schematic view of a rollconstruction embodying the present invention; and

FIG. 2 is an exaggerated cross-sectional, broken-away detail view of oneof the rolls of the construction of FIG. 1.

SPECIFIC DISCLOSURE In a paper making process involving the presentinvention, the initial wet sheet 10, is formed by casting a diluteaqueous slurry of cellulose fibers onto an endless wire screen 11, as isshown in FIG. 1. In accordance with the present invention a so-calledlumpbreaker roll 14, which is a press roll embodying the presentinvention, serves to contact the advancing paper sheet in such a way asto flatten uneven agglomerations of fibers in various portions of theadvancing sheet. The sheet next advances onto an endless felt 12. Thewet sheet and the felt advance into engagement between a series of pressrolls, two of which are shown at 16, 18, after the sheet is separatedfrom screen 11 at 15. Then the wet sheet advances between the nips of aseries of press rolls, two of which are shown at 20, 22. When advancingover wire screen 11, on felt 12 and in contact with the various pressrolls, generally the moisture content by total weight of the sheet is inexcess of 35%. The rolls in direct contact with the Wet sheet, duringthis time, are characterized by exceptional release properties inaccordance with the present invention. It will be understood that suchdirect contact rolls may be above and/ or below the advancing papersheet.

As shown in FIG. 2, each of press rolls 14, 20 and/or 22 is shown ashaving a metal core 24 and an elastomeric veneer 26. The metal core, forexample, is in the form of a solid or hollow cylinder composed of metalsuch as steel or cast iron, or other dimensionally stable material. Theveneer contains a matrix of an elastomer 28 and dispersed, randomlydistributed fiber strands 30. Preferably, the elastomer is syntheticand, most advantageously, is selected from the class consisting ofchloroprene, chlorosulfonated polyethylene and ethylene propyleneterpolymer. Preferably, the fiber strands are composed of a hydrophobicsynthetic polymer, and, most advantageously, are selected from the classconsisting of polyesters, polyamides and acrylics. Best results havebeen achieved with linear polyamides such as polyhexamethyleneadipamide. For present purposes, the term hydrophobic is applied to amaterial having a regain of moisture from a bone dry condition of lessthan 5% based on original bone dry weight in an atmosphere having 65%relative humidity at F. Preferably, by total weight of the combination,the strands range from 0.5 to 10.0% and the elastomer ranges from 99.5to For best results, the strands range from /2 to 5 denier and from to 2inches long. Preferably the final composition ranges from 20 to 200plastometer, /s" ball, Pusey and Jones.

EXAMPLE I A press roll of the foregoing type was produced as follows.Polyhexamethylene adipamide strands, 1 /z denier and 1% long, wereuniformly carded into a mass of uncured chloroprene rubber. Theresulting dispersion of strands in chloroprene rubber was such that, bytotal Weight, the strands were approximately 5% and the chloroprenecomposition was approximately The chloroprene composition Was formulatedin accordance with typical practice to give a hardness of 25plastometer, /a inch ball, Pusey and Jones. An iron core, 34 inches indiameter by 184 inches in length, was roughened by grit blasting andcoated with cement in accordance with well established roll coveringtechniques. The foregoing formulation was applied in a 1 inch thicknessonto the iron core and cured, finished and ground in accordance withwell established roll manufacturing techniques. Examination revealedthat the ends of the strands penetrated through the ground surface ofthe chloroprene roll cover. This ground surface was characterized byexceptional release characteristics with respect to wet paper sheet incontact therewith.

plastometer, /8 inch ball, Pusey and Jones, with similarly excellentresults.

3 OPEMTION AND CONCLUSION The superior release characteristics of therolls illustrated above are believed to be based, at least in part, .onthe effect of the free ends of the fiber shreds on the surface tensionof a film of water on the roll. These free ends interrupt the uniformwetting of the roll by the wet paper sheet and, thereby, interrupt theuniformity of the surface tension of the layer of water that otherwisewould exist on the roll cover. The result is that cellulose fibers fromthe wet paper sheet, which are swollen with moisture, have a greatlydecreased tendency to adhere to the surface of the roll.

I Since certain changes may be made in the foregoing disclosure withoutdeparting from the scope of the invention sheet between 'a'pair' 'ofpressure surfaces,'at least one of polyamides and acrylics, said matrixbeing selected from the class consisting of chloroprene,chlorosulfonated polyethylene and ethylene propylene terpolymer.

2. The roll of claim 1 wherein said strands are composed of a. linearpolyamide, being approximately within the ranges of to 5 denier indiameter and to 2 inches in length, said strands by total-weight of saidveneer ranging approximately from 0.5 to 10% and said elastomeric matrixby total weight of said veneer ranging approximately from 99.5 .to 90%.

3. A process for squeezing water from a wet paper sheet, said processcomprising the steps of advancing the paper said surfaces beingconstituted by an elastomeric matrix interrupted by hydrophobic,synthetic, polymeric fiber strands which penetrate and protrude throughthe outer surface of said elastomeric matrix, reducing thesurfacetension of water in contact with said one of said surfaces by operationof said fiber strands, and freely advancing said paper sheet fromcontact with said one of said surfaces, said strands being composed of ahydrophobic synthetic polymer selected from the class consisting ofpolyesters, polyamides and acrylics, said matrix being selected from theclass consisting of chloroprene, chlorosulfonated polyethylene andethylene propylene terpolymer.

4. The process of claim 3 wherein said strands are composed of a linearpolyamide, being approximately within the ranges of to 5 denier indiameter and to 2 inches in length, said strands by total Weight of saidveneer ranging approximately from 0.5 to 10% and said elastomeric matrixby total weight of said veneer ranging approximately from 99.5 to

References Cited UNITED STATES PATENTS 3,262,840 7/1966 Hervey 162-2052,801,461 8/1957 Kiisters 29125 X 2,878,778 3/1959 Kiisters 2912S X3,069,304 12/1962 Fahrbach et a1. 29125 X 3,184,828 5/1965 Dames 29132 XOTHER REFERENCES Tappi magazine, March 1965 issue, vol. 48, No. 3, p.13A.

Materials in Design Engineering magazine, September 1957 issue, pp. 143and 144.

BILLY I. WILHITE, Primary Examiner US. Cl. X.R. 33125, 169

